The invention relates to a pipe tapping valve which can be attached to a pipe, especially by welding, and which comprises a support stub in which a drill bit is disposed for axial movement and to which a nipple is attached.
A pipe tapping valve of this kind is disclosed in Freidel, German Patent No. DE 3,830,395 C1 and can be attached to a plastic pipe, especially by welding. The pipe tapping valve comprises a branch in which a drill bit designed for drilling the pipe is disposed for axial movement. A sleeve with an internal thread is sealingly integrated into the branch in a non-rotatable manner. The drill has an external thread engaging the internal thread, as well as an internal hexagon for a tool. When the inserted tool is rotated, the drill performs an axial feed for drilling through the wall of the pipe connected to the valve. Also, at least one sealing ring is provided in order to prevent the escape of the medium flowing through the pipe after it has been drilled. This pipe tapping valve has proven to be very useful in many cases, but requires a substantial expenditure of material and effort to manufacture it.
Lang, German Patent No. DE 4,039,353 C1 discloses a system for shutting off a pipe, on the outside surface of which an upper part can be fastened, especially a metal clamp. The upper part contains a support stub to which the housing of a pipe tapping valve can be joined. The pipe tapping fitting contains a threaded spindle whose external thread engages an internal thread in the housing. A drill bit can be attached to the threaded spindle, which is also configured as a stopper. When the threaded spindle is rotated the drill is advanced axially in order to drill into the plastic pipe. The drill contains an external thread which provides for the anchoring of the drill bit or stopper in the pipe after drilling. After the drilling is done the anti-rotational connection of the drill bit is released from the threaded spindle and the housing is removed from the upper part, the drill bit remaining in the pipe as a stopper.
Furthermore, a pipe tapping valve made of plastic is disclosed in Pessia, U.S. Pat. No. 4,063,844, in which a support stub contains an internal thread for the drill bit. The drill bit furthermore has an internal hexagon for a hexagonal wrench and when it is turned the drill bit is given an axial feed, although a considerable torque has to be applied. The internal thread of the support stub extends over its entire length, and after the pipe has been drilled, the sealing is accomplished only by the threaded connection between the drill bit and the support stub. A not inconsiderable leakage must be expected, which is undesirable particularly in the case of pipes carrying gas.